The present invention relates to new polymeric particles useful in latex agglutination medical diagnostic applications. More particularly, the invention is directed to vinyl aromatic monomer/vinyl acrylate ester monomer copolymers, which are modified by a protein binding modifying monomer. These modified latex particles can bind a protein to the surface of the particle, and can be used to form antibody/antigen complexes used in immunoassays.
Latex particles have been used in diagnostic testing such as agglutination tests, which serve as a means to detect the presence or absence of an antibody or antigen itself. Conceptually, an antibody or antigen is bound to the surface of a latex particle which can subsequently react in body fluid, e.g., blood serum, urine and the like. Generally, the antigen bound to the latex particle is introduced to a body fluid containing the corresponding antibody. The antibody undergoes an association reaction with the antigen, forming an antibody/antigen/latex complex, which, via a bridging mechanism, aggregates with other similar complexes. These aggregates can be detected visually or by techniques which measure scattered light. This type of agglutination test is designated to detect the presence of aggregates formed, or absence of aggregates with a particular antibody. Such agglutination tests are useful for the detection of infectious agents, theraputic drugs, drugs of abuse, circulating antibodies, hormones, lipids and the like.
Latex particles used in diagnostic tests must have certain desired properties in order to function properly. For instance, the latex particles must be capable of binding an antigen to its surface, to allow the bound antigen to undergo an aggregation reaction with its corresponding antibody. The latex particle must also be insensitive or inert to other components or proteins present in the body fluid. Additionally, there must be an accurate technique for detecting the aggregation reaction.
A fundamental problem in developing latex particles for agglutination tests is not in the binding an antigen to its surface, but is preparing a particle which will specifically agglutinate in a particular body fluid. The latex particle must avoid nonspecific interaction with other serum components. If the latex particle strongly absorbs the undesirable protein components of the blood serum, then the particle would be unable to undergo specific agglutination based on an antibody/antigen reaction, or if the antibody/antigen reaction occurs, the complex does not aggregate, via a bridging mechanism, with other similar complexes. In either case, incorrect results would occur, giving either false positives or false negatives depending upon how the test is designed.
The fundamental problem in the development of latex diagnostic particles of the type described is preparing latex particles which is specifically limited to a reactive antibody or antigen, which is capable of undergoing specific agglutination in blood serum. At the present time there exists only a limited number of diagnostic tests that can be reliably made with the type of technique described. Generally, the properties of latex particles heretofore available have not been suitable for a wide range of diagnostic applications.
Thus, it is highly desirable to provide improved polymeric particles useful in latex agglutination medical diagnostic applications and having the capability of binding specific antibodies to provide improved agglutination test methods, and finding utility in a broader variety of diagnostic applications.